The present invention relates to a hand apparatus for an article assembly robot or a hand apparatus for gripping an article used for an article conveying system.
As a conventional hand apparatus attached to a robot, an apparatus comprising fingers for gripping only one kind of article is known.
As a hand apparatus comprising a function of adjusting an article to a correct gripping position in order to reliably hold an article with fingers, Japanese Patent Laid-Open (Kokai) No. 61-256004 is known.
Japanese Patent Publication No. 62-18317 discloses an arrangement having a hand body, and a pair of pawls, one-end portions of which are attached to the hand body, and which are moved by an actuator relative to the hand body so as to grip an article, wherein a suction hole for chucking an article is formed in one pawl, and the suction hole is coupled to a vacuum source.
Furthermore, Japanese Patent Publication No. 51-6939 discloses an apparatus having a plurality of pawls, which are driven by a hydraulic cylinder, in order to grip objects to be gripped, which have different shapes.
However, in these conventional hand apparatuses, a gripping apparatus which has a function of conveying a plurality of kinds of articles to one assembly line, and sequentially gripping the articles to assemble them, cannot be met.
More specifically, as shown in FIG. 8, in an assembly process of an aperture unit used in a camera, the above-mentioned gripping apparatus is required. An aperture unit shown in FIG. 8 is constituted by an aperture support ring (a), aperture blades (b), and an operation ring (c) for pivoting the aperture blades (b). The aperture support ring (a) and the operation ring (c) are molded and formed of a metal or a relatively hard plastic material. Therefore, the aperture ring (a) and the operation ring (c) can be pressed and gripped at their side surfaces by finger members.
On the other hand, each aperture blade (b) is normally formed of a metal. The thickness of each aperture blade (b) is very small, and is about 1/100 mm. The aperture blades (b) are required to have strict flatness. Upon rotation of the aperture blade (b) itself and a stack of the aperture blades (b), bending and warp of blades are strictly regulated. For this reason, the side surfaces of the aperture blades (b) cannot be pressed and gripped since it may cause warp or bending of the blades.
In order to automate and unman an assembly of the above-mentioned aperture unit, the aperture support ring (a), the aperture blades (b), and the operation ring (c) are sequentially gripped by a gripping apparatus, and are automatically assembled by an assembly station. However, since these articles must be gripped in different modes, it is difficult to grip these articles by a single gripping apparatus. For this reason, a plurality of types of gripping apparatuses must be prepared in correspondence with the gripping modes, thus posing problems of cost and installation space.
If articles of different gripping modes are to be gripped in one gripping mode, the articles may be damaged by the gripping operation.
In the assembly station, e.g., fingers of an assembly robot, a gripping apparatus is selected and replaced in accordance with a gripping mode of an article. For this reason, the assembly robot must have a finger detaching apparatus between a robot arm and a hand apparatus. As a result, its structure is complicated and prolonged working time is required for replacing fingers, resulting in poor workability.